President Bashar al-Assad could survive for some time and the West does not
have a "clear mechanism" for removing Syria's regime, senior
Western diplomats conceded on Wednesday.

Despite Europe, the United States and most of the Arab world trying to maximise the pressure on Mr Assad, diplomatic sources believe there is no imminent prospect of his downfall.

President Barack Obama said on Tuesday that Mr Assad's overthrow was a question of "when, not if", but diplomats say the regime is still convinced that it can defeat the opposition.

"There are various scenarios for change, but there isn't a clear mechanism right now for achieving that," said one.

While economic sanctions have been imposed, Western powers have ruled out direct military intervention. The United Nations Security Council has so far failed to pass a resolution on Syria after Russia and China vetoed an earlier draft based on an Arab League initiative that would have called on Mr Assad to stand down. Another draft resolution is being circulated at the UN which call on the Syrians to allow humanitarian agencies to work freely, and contain some language about reform.

Simon Collis, the British ambassador to Syria, who has returned to London following the closure of the embassy in Damascus over security concerns, yesterday said he held to the view that Mr Assad would more likely than not be gone by the end of the year.

But he could not rule out the prospect of Mr Assad surviving the revolt. "I can't say that is impossible from an analytical point of view," he said. "I certainly don't think it's likely and certainly not desirable."

The cautious assessment came as Baroness Amos, the UN under-secretary for humanitarian affairs, was taken by Syrian officials for a 45-minute tour of Baba Amr, the previously rebel-held district of the city of Homs which suffered 26 days of continuous bombardment.

Aid workers from the Syrian Arab Red Crescent were also allowed to distribute food and medical supplies in the area for the first time since it fell to the army last week. They found most residents had fled.

Lady Amos, who was initially denied entry to Syria last week, is on a three-day mission to persuade authorities to grant unfettered access for aid workers to needy civilians caught up in violence.

Earlier, she met with Walid al-Moualem, foreign minister, in Damascus. He told her Syria was trying to meet the needs of all citizens despite the burdens imposed by "unfair" Western and Arab sanctions, the state news agency SANA said.

While her visit is a concession to international opinion, it has been conducted on Mr Assad's terms and demonstrated how he has been able to manipulate access by outside observers and journalists to a large degree.

For all the horror at atrocities against civilians, the Syrian president retains the support of most of the ruling elite, while the armed opposition is weak.

Officials in Western and Arab League governments concede that the regime is unlikely to collapse inwardly.

The leadership is encouraged, they say, by its ability to crush the uprising in key locations such as Homs, and retain its control of the two major cities, Damascus and Aleppo, even if this has come at the cost of some 7,000 lives.

"The regime thinks it can still win, it sees everything through the security prism," said Mr Collis.

Officials acknowledge that the forces undermining Mr Assad are a long way from attaining "critical mass". Despite a steady trickle of defections, most of the army remains loyal.

Some 70 per cent of the officer corps is from Mr Assad's Alawite sect, while the number of defections to the rebels - probably 10,000 or 20,000 soldiers – is only a fraction of the army's total active strength of 220,000.

The defectors have generally been rank-and-file troops and junior NCOs, not high-ranking officers. Unlike during Libya's uprising against Col Muammar Gaddafi, there have been no defections by entire military units.

The Free Syrian Army, an armed opposition movement, has inadequate weapons, no proper command structure and its leaders are exaggerating the number of insurgents. Although Saudi Arabia has publicly advocated arming the rebels, the FSA is still ill-equipped and Western countries have ruled out the supply of lethal equipment.

Toby Dodge, a Middle East expert at the International Institute for Strategic Studies, yesterday said that Syria's insurgents could not defeat Mr Assad's forces.

They were more of an "irritant" to the regime than a threat, he added. "What we're in is a form of bloody attrition," he warned.

Meanwhile, Mr Assad has benefited the diplomatic support of Russia and China and the direct supply of weapons, cash, expertise and military advice from Iran.

Two of his neighbours, Iraq and Lebanon, are not enforcing economic sanctions against Syria; even Turkey, a voluble critic, has refrained from taking every possible step to tighten the economic noose.

By protecting Syria at the UN, Russia has effectively given Mr Assad a "green light" to continue his military campaign against the rebels, said one Western diplomat.

Mr Assad's Achilles Heel is the economy, which is buckling under the weight of isolation and sanctions, especially a European Union oil embargo.

Rising unemployment and lack of basic supplies are reducing the regime's popular support, particularly among the Sunni mercantile class in the major cities.